Precipitation falling from clouds. What clouds bring rain Brief summary of the project

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Geography teacher Khabarova N.V. PRECIPITATION

rain snow hail frost dew frost ice falling from clouds falling from the air

Why doesn't every cloud rain? If a cloud consists of tiny droplets of water, then they are so light that they cannot fall to the earth's surface. Water droplets in a cloud are constantly in motion. They collide, stick together and gradually become larger and heavier. When the droplets become so heavy that they cannot stay in the air, it begins to rain. Raindrops must have a diameter of at least 0.5-5mm

why does it snow? For snow to form, the temperature in the cloud must be 0 degrees.

Why does hail fall? Hailstones form in cumulonimbus clouds. Water droplets in a cloud, under the influence of moving air, either rise up or fall down. At the same time, they fall into the upper part of the cloud, where t is below 0. The droplet turns into a piece of ice. The piece of ice sinks to the bottom of the cloud and becomes covered with water. Then it rises again, a layer of ice freezes on it. Eventually the ice-hailstone becomes so heavy. that falls on the earth's surface. The sizes of hailstones vary greatly.

precipitation falling from the air frost frost A thin layer of ice crystals deposited from water vapor on the cooled surface of soil, grass, objects. It usually forms on quiet, clear nights in autumn or spring. Deposition of ice in the form of crystals on tree branches and wires that occurs during fog, usually in calm frosty weather.

precipitation falling from the air dew ice Deposition of a dense layer of ice on tree branches, wires, poles when supercooled drops of rain or fog freeze. Formed at t from 0 to -3 near the earth's surface. NOT TO BE CONFUSED WITH ICE!!! (Slippery Road) Due to air cooling, water vapor condenses on objects near the ground and turns into water droplets. This usually happens at night. Quite strong cooling of the lower layers of air occurs when, after sunset, the earth's surface quickly cools through thermal radiation.

measuring the amount of precipitation The amount of precipitation is measured using a precipitation gauge. A rain gauge looks like a bucket. It is installed on a pole and surrounded with special protection so that the wind does not blow precipitation to the side. When determining precipitation, water from the precipitation gauge is poured into a special measuring glass and the thickness of the water layer is determined in millimeters. How to determine how much snow has fallen?

Precipitation charts The amount of precipitation for all months of the year is annual quantity precipitation. Average long-term precipitation and its pattern are reflected in precipitation charts. determine: 1.Annual precipitation 2.Precipitation regime 3.Which month received the most precipitation? 4.Which month had the least rainfall?

nature of precipitation Rainfall is intense, short-lived, and covers a small area. Drizzling precipitation (fine droplets, as if suspended in the air) Provides little moisture. Convective precipitation. Characteristic of the hot zone. Where there is strong heating and evaporation. Covered precipitation (of medium intensity) uniformly covers large areas.

nature of precipitation Frontal precipitation is formed when two air masses with different temperatures and other properties meet; they fall from warmer air, forming cyclonic vortices. Orographic precipitation Falls on the windward slopes of mountains, especially high ones. They are abundant if the air comes from the warm sea.

Homework: Make a diagram in your notebook “Types of Atmospheric precipitation» Paragraph 41

Clouds are a wonderful predictor of upcoming weather changes if there is no television or radio nearby. It’s not even worth talking about receiving a forecast by cell phone - this is a deception of cellular operators.

Upper clouds

There are three subtypes of clouds classified as upper level clouds. The general name of the group is cirrus.

Spindrift clouds. Such clouds never carry precipitation. But if they are present in the sky, it is necessary to remember that within a period of 12 hours to two days a significant change in weather and rain is possible.

Cirrocumulus. When such clouds appear, remember that a thunderstorm with heavy rain is expected in a maximum of eight hours.

Cirrostratus. If such a sign appears, then over the next three days we can expect a strong change in the weather towards cooling, which is preceded by rain.

Mid-level clouds

Mid-level cumulus and stratus clouds are located at an altitude of 2 to 6 kilometers from the earth's surface. The probability of precipitation from them is extremely low, but if they appear, certain conclusions can be drawn.

Altocumulus clouds. ABOUT nor do they predict worsening weather, wind and prolonged rain with thunderstorms.

Altostratus clouds. In the summer it threatens us with a little “mushroom” rain, but in the winter it will definitely bring snowfall.

Low clouds

These are heavy, “leaden” clouds. They are clumsy and heavy, so they do not rise higher than 2 kilometers from the ground.

Stratocumulus. Often such clouds bring us drizzle and fog, and in winter fine grains of snow.

Stratus clouds. In summer, light drizzle and bad weather are sometimes possible, and in winter you should not expect any precipitation at all.

Nimbostratus.

Their height ranges from 100 meters to 1 kilometer. Its appearance is preceded by a strong gusty wind, followed by heavy downpours and a sharp cooling of air masses.

Cumulus clouds. These are true friends of good weather. If you saw them in the sky, tomorrow it will be sunny and nice.

Cumulonimbus clouds. They will definitely bring a thunderstorm with possible hail and a sharp gale, and there is a possibility of the formation of air vortices.

The probability of prediction from clouds, although not 100 percent, rarely fails.

Precipitation falling from clouds

Atmospheric phenomena

As already said, atmospheric phenomena– this is precipitation (rain, snow, drizzle, hail), dew, frost, ice, fog, haze, haze, dust storm, thunderstorm, tornado, etc.

Precipitation falling from clouds

Rain is precipitation that falls in the form of drops. Individual drops of rain, falling into the water, always leave a trail in the form of a diverging circle, and on a dry deck - a trail in the form of a wet spot.

Cover rain - precipitation falling from nimbostratus clouds. It is characterized by a gradual beginning and end, precipitation is continuous or with short breaks, but without sharp fluctuations in intensity, and in most cases the clouds cover the entire sky with a continuous, homogeneous cover. Sometimes weak and short continuous rain can also fall from altostratus, stratocumulus and other clouds.

Rain shower - rain, characterized by the suddenness of the beginning and end of the fall, a sharp change in intensity. The name "heavy rain" refers to the nature of the rainfall, and not the amount of precipitation that falls, which may be insignificant. View of the sky during heavy rain; The clouds are predominantly cumulonimbus, sometimes blue-lead in color, with temporary clearings occurring. Rain showers are often accompanied by thunderstorms.

Drizzle - precipitation that falls in the form of very small droplets. The droplets are so small that their fall is almost invisible to the eye; they are suspended in the air and participate even in its weak movement. Drizzle should not be mixed with light rain, the drops of which, although very small, can be observed falling: drops of drizzle settle slowly and their fall is imperceptible. When it drizzles, there are no circles on the water. Drizzle usually falls from stratus clouds or fog.

Snow - precipitation in the form of individual snow crystals or flakes, sometimes reaching large sizes

Cover snow- precipitation falling from nimbostratus clouds continuously or with short breaks.

In most cases, clouds cover the entire sky solid uniform cover. Cover snow can also fall from altostratus, stratocumulus, stratus, etc.

Shower snow- snow, characterized by the suddenness of the beginning and end of the fall, sharp fluctuations in intensity and the short duration of its heaviest fall. The appearance of the sky during heavy snow: gray or dark gray cumulonimbus clouds alternating with short-term clearings.

In the polar seas there are often frequent, very short, but heavy snowfalls, which are called snow charges.

Wet snow - precipitation that falls in the form of melting snow or sleet.

Snow pellets - precipitation that falls in the form of opaque snow grains of white or matte white color, spherical in shape, with a diameter of 2 to 5 mm. The grains sometimes have the shape of a cone with a segment-shaped base. They are small, fragile and easily crushed by fingers. Snow pellets fall mainly at temperatures around 0°C, often before or simultaneously with snow. In spring and autumn, snow pellets often fall from cumulonimbus clouds in short showers during squalls in cold air masses.

Snow grains - sediments in the form of sticks or grains, similar to snow pellets, but much smaller, matte white in color. The diameter of the grains does not exceed 1 mm. Snow grains usually fall in small quantities and mostly from stratus clouds.

Ice grains - precipitation that falls in the form of small transparent ice grains, in the center of which there is a small white opaque core. The diameter of the grains does not exceed 3mm . The grains are hard and require little force to crush. When the air temperature is above 0° C, their surface is wet. Ice pellets usually fall from cumulonimbus clouds, often along with rain, and are observed mainly in spring and autumn.

hail- precipitation that falls in the form of pieces of ice of various shapes. Hailstone cores are usually opaque, sometimes surrounded by a transparent layer or several transparent and opaque layers. The diameter of hailstones is about 5 mm, in rare cases it reaches several centimeters. Large hailstones reach a weight of several grams, and in exceptional cases - several tens of grams. Hail falls mainly in the warm season from cumulonimbus clouds and is usually accompanied by heavy rain. Severe large hail is almost always associated with thunderstorms and strong winds.

freezing rain- precipitation, which is small, hard, completely transparent ice balls with a diameter of 1 to 3 mm, formed from raindrops when they freeze in the lower layers of the atmosphere. They differ from ice pellets by the absence of an opaque white core.

Clouds foreshadowing a change in weather

Cirrostratus fibratus (Cs fib)

Cirrostratus fibratus (Cs fib) is a white veil with a weak wavy structure. Main feature clouds is their arrangement in the form of parallel, seemingly converging ridges. Cloudiness usually covers the entire sky. The height of the base in middle latitudes is about 6-8 km, the thickness of the layer is from 100 meters to several kilometers. A bright halo around the sun and moon is often observed. Shines through them blue sky, and at night - bright stars. Sometimes Cs are so thin and uniform that they can only be detected by the presence of a halo. Precipitation from Cs does not reach the ground and only produces light snow or ice needles at very low temperatures. Formed as a result of adiabatic cooling of air during its upward movement in the upper troposphere in zones atmospheric fronts. The appearance of cloudiness Cs fib may foretell a change in the weather, and rain in mid-latitudes.

Cumulus congestus (Cu cong)

Powerful cumulus - Cumulus congestus (Cu cong) clouds highly developed vertically. Some of them are partially torn, shaggy, in the form of towers tilted to the side. The thickness of the clouds is 1.5 - 2 times greater than the base of the cloud. The top of the cloud is dazzlingly white, swirling, the base is darkened. In the central part, cumulus clouds completely cover the sun, while the edges shine through, and crowns often form. There is usually no precipitation. They are formed mainly as a result of powerful upward air currents caused by uneven heating of the underlying surface. Cu cong's development summer time leads to the development of cumulonimbus clouds and heavy rainfall.

Altocumulus (Ac)

Altocumulus (Ac) clouds are typical for the warm season. It is located, as a rule, above the slopes facing the sun. Sometimes they reach the stage of powerful cumulus clouds.

Cirrus uncinus (Ci un)

Cirrus uncinus (Ci un). These are relatively small parallel filaments of clouds with a comma-shaped bend at the end. Typically composed of ice crystals that arise from supercooled water droplets. They are distinguished by their greater extent and the fact that they do not fill the entire sky. Most often, clouds are observed in the presence of an upward flow of air during the advance of a warm front. Ci un are harbingers of changes in the weather. The height of the base in temperate latitudes is 7-10 km, in the tropics they reach 17-18 km. The clouds are transparent, the sun, moon and bright stars shine through them, and sometimes the blue sky. During the day they do not reduce illumination.

Precipitation does not fall from these clouds. The formation of cirrus clouds occurs due to air cooling during upward movement in the middle troposphere in the zone of atmospheric fronts. In the cooling air, water vapor sublimates and ice crystals form. Small ice crystals fall very slowly and can be transported to higher levels by rising air movements.

In the evening, after sunset, Ci un remain illuminated for a long time, taking on a silvery, then golden or reddish color. In the morning, before sunrise, they are the first to be colored by the sun.

Cumulus humulus (Cu hum)

Cumulus humulus (Cu hum) are scattered across the sky, rather dense clouds with clear horizontal bases, little developed vertically. They are observed mainly in the warm season. They usually appear in the morning, reach their greatest development around midday and spread out in the evening, turning into stratocumulus evening clouds. Occasionally observed in temperate latitudes in winter. The presence of Cu hum indicates established good weather and the clouds are called “fair weather clouds”

Altocumulus floccus (Ac fl)

High cumulus floccus - Altocumulus floccus (Ac fl) - are white cloud flakes torn at the edges, relatively quickly changing their shape. They are formed at an altitude of 2-6 km due to convective air movement in the layer above 2 km. Precipitation can fall in the form of individual drops or snowflakes. Unlike cirrocumulus clouds, they can have shadowed parts, which typically consist of water droplets.

Altocumulus clouds usually occur as a result of rising warm air masses, as well as the arrival of a cold front that pushes warm air upward. Therefore, the presence of altocumulus clouds on a warm and humid summer morning often heralds the imminent appearance of thunder clouds or a change in weather.

According to the international classification, there are 10 main types of clouds of different tiers.

> UPPER LEVEL CLOUDS(h>6km)
Spindrift clouds(Cirrus, Ci) are individual clouds of a fibrous structure and a whitish hue. Sometimes they have a very regular structure in the form of parallel threads or stripes, sometimes on the contrary, their fibers are tangled and scattered across the sky in separate spots. Cirrus clouds are transparent because they consist of tiny ice crystals.

Often the appearance of such clouds heralds a change in the weather. From satellites, cirrus clouds are sometimes difficult to see.

Cirrocumulus clouds(Cirrocumulus, Cc) - a layer of clouds, thin and translucent, like cirrus, but consisting of individual flakes or small balls, and sometimes as if from parallel waves.

These clouds usually form, figuratively speaking, a “cumulus” sky. They often appear along with cirrus clouds. Sometimes visible before storms.

Cirrostratus clouds(Cirrostratus, Cs) - a thin, translucent whitish or milky cover, through which the disk of the Sun or Moon is clearly visible. This cover can be uniform, like a layer of fog, or fibrous. On cirrostratus clouds, a characteristic optical phenomenon is observed - a halo (light circles around the Moon or Sun, false Sun, etc.). Like cirrus, cirrostratus clouds often indicate the approach of severe weather.

> MIDDLE LEVEL CLOUDS(h=2-6 km)
They differ from similar lower-level cloud forms in their high altitude, lower density, and greater likelihood of having an ice phase.
Altocumulus clouds(Altocumulus, Ac) - a layer of white or gray clouds consisting of ridges or individual “blocks”, between which the sky is usually visible. The ridges and “blocks” that form the “feathery” sky are relatively thin and are located in regular rows or in a checkerboard pattern, less often - in disorder. "Cirrus" skies are usually a sign of pretty bad weather.

Altostratus clouds(Altostratus, As) - a thin, less often dense veil of a grayish or bluish tint, in places heterogeneous or even fibrous in the form of white or gray shreds all over the sky. The Sun or Moon shines through it in the form of light spots, sometimes quite faint. These clouds are a sure sign of light rain.

> LOWER CLOUDS(h

The main amount of precipitation in mid-latitudes comes from nimbostratus clouds. But in the initial phase of their development, no precipitation comes from the clouds; in the mature stage, they give continuous precipitation (i.e., over a large area at the same time), and in the destruction stage, precipitation stops again. http://www.sgu.ru/ie/geo/meteo/R3.htmAccording to the physical conditions of formation, precipitation is usually divided into three large genetic types: 1. Cover, frontal2. Storm, intramass3. DrizzlingDepending on the type, precipitation is divided into liquid, solid and mixed. Cover precipitation is formed in cloud systems of warm and cold fronts and in cloud systems of occlusion fronts. They fall from nimbostratus, altostratus and cumulonimbus clouds. The longest continuous precipitation occurs during the passage of occlusion and warm fronts. Heavy precipitation usually lasts for a day or more and covers vast areas, on the order of hundreds of thousands of square kilometers. Almost all meteorological stations located on flat areas record approximately the same amount. Coverage precipitation falls in the form of rain and snow and is observed mainly in temperate and high latitudes at any time of the year. Rainfall occurs mainly due to the development of intramass convection in unstable stratified air masses. Rainfall also forms in cloud systems of cold and sometimes warm fronts. Rainfall is characterized by high intensity and relatively short duration. Even showers that fall from frontal cumulonimbus clouds last no more than a few hours. An exception to the above regarding the duration of rainfall is that falling from the cumulonimbus clouds of the Intertropical Convergence Zone, as well as during the monsoon. Rainfall of this type continues for days and weeks, sometimes weakening and then intensifying again. Intramass storm precipitation in temperate latitudes, even over flat areas, is characterized by very large spatial heterogeneity. The spatial heterogeneity of rainfall is manifested both in the fact of its occurrence and in its intensity and quantity. This is due to the horizontal scale of the convective cells that form the cumulonimbus cloud, as well as the structure of the cumulonimbus cloud. Maximum dimensions Convective cells, sometimes called "supercells", rarely exceed 100 km. Within these limits of linear dimensions, the spatial heterogeneity of intramass rainfall is formed. Rainfall in temperate latitudes occurs in the warm season, and in tropical latitudes it occurs constantly. Rainfall falls in the form of rain, snow, hail, and snow pellets. Rainfall is characterized by a rapid increase in intensity at the beginning, large fluctuations and an abrupt cessation. The intensity of rainfall is maximum; in the tropics and subtropics it can reach 25-30 mm/min. Drizzle falls in the form of very small drops, snow grains and fine snow. They belong to intramass precipitation, sometimes preceding the passage of a warm front, falling from altostratus clouds. Drizzle falls from stratus or stratocumulus clouds. The drops, snowflakes or ice crystals that fall from them are very small and their falling speed is so low that they appear to be suspended in the air. Drizzling precipitation is formed in stably stratified air masses when they are cooled to the dew point due to radiation cooling, when air masses mix over areas of the earth's surface that have different temperatures, when warm air advects onto a cold underlying surface. In this case, fog is formed, that is, layered clouds, the lower boundary of which coincides with the surface, and drizzle falls from them. http://meteoweb.ru/phen040.php

Under certain conditions, precipitation falls from the clouds, i.e. droplets or crystals of such large sizes that they can no longer be kept suspended in the atmosphere. The most famous and important are rain and snow. However, there are several other types of precipitation that differ from the typical forms of rain and snow.

Both rain and snow fall primarily from upslip clouds and convection clouds. Depending on this, the nature of precipitation will be different.

From the ascending clouds (nimbostratus and altostratus) associated with fronts, blanket precipitation falls. This is long-term precipitation of medium intensity. They fall immediately over large areas, on the order of hundreds of thousands of square kilometers, relatively evenly and for quite a long time (hours and tens of hours). Precipitation is observed at all stations or at most stations on large territory; Moreover, the precipitation amounts at individual stations do not differ too much from one another. The largest percentage of the total precipitation in temperate latitudes is made up of continuous precipitation.

Cumulonimbus clouds associated with convection produce heavy but short-lived rainfall. Immediately after they begin, they can gain great intensity, but they end just as abruptly. Their comparative short duration is explained by the fact that they are associated with individual clouds or with narrow zones of clouds. In cold air masses moving over warm earth's surface, isolated showers sometimes last only a few minutes over any given point. During local convection over land in the summer, when cumulonimbus clouds are particularly extensive, or during the passage of fronts, showers sometimes continue for hours. According to observations in the USA, the average area simultaneously covered by the same heavy rain is about 20 km 2.

During short-term precipitation, rainfall can also provide a small amount of water. Their intensity fluctuates greatly. Even in the same event of rain, the amount of precipitation can vary by 50 mm at a distance of only 1-2 km. Rainfall is the main type of precipitation in low tropical and equatorial latitudes.

In addition to heavy and torrential precipitation, there is also drizzle precipitation. This is intramass precipitation falling from stratus and stratocumulus clouds, typical of warm or local stable air masses. The vertical thickness of these clouds is small; therefore, in the warm season, precipitation can fall from them only as a result of the mutual fusion of droplets. Liquid precipitation - drizzle - consists of very small droplets. In winter, at low temperatures, these clouds may contain crystals. Then, instead of drizzle, small snowflakes and so-called snow grains fall out of them.

As a rule, drizzle does not produce significant daily amounts. In winter they do not noticeably increase the snow cover. Only in special conditions, for example in the mountains, drizzle can be more intense and abundant.

Forms of precipitation

Rain consists of droplets with a diameter of more than 0.5 mm, but not more than 8 mm. With larger droplet sizes, they break into pieces when falling. In torrential rains, the drop size is larger than in regular rains, especially at the beginning of the rain. At subzero temperatures, rain sometimes falls in supercooled form; In contact with the earth's surface, supercooled drops freeze, covering it with an ice crust.

Drizzle consists of droplets with a diameter of about 0.5-0.05 mm with a very low precipitation rate; they are easily transported by the wind in a horizontal direction. Snow is made up of complex ice crystals (snowflakes). Their forms are very diverse depending on the conditions of their formation. The basic shape of snow crystals is a six-pointed star. Stars are made from hexagonal plates because the sublimation of water vapor occurs most quickly at the corners of the plates, where the rays grow; on these rays, in turn, branches are created. The diameters of falling snowflakes can be very different, but in general they are on the order of millimeters. When snowflakes fall, they often stick together into large flakes. At temperatures close to zero and above zero, sleet or snow and rain falls. It is characterized by large flakes.

From nimbostratus and cumulonimbus clouds at subzero temperatures more grains, snow and ice, fall. It looks like round (sometimes cone-shaped) nucleoli with a diameter of 1 mm or more. Most often, cereals are observed at temperatures not very far from zero, especially in autumn and spring. Snow pellets have a snow-like structure: the grains are easily compressed with your fingers. The kernels of ice grains have a frozen surface; It is difficult to crush them; when they fall to the ground, they jump.

Instead of drizzle, snow grains fall from stratus clouds in winter - small grains with a diameter of less than 1 mm, reminiscent of semolina.

At low winter temperatures, sometimes ice needles - crystals in the form of hexagonal prisms and plates without branches - fall out of the clouds of the lower or middle tier. During significant frosts, such crystals can appear in the air near the earth's surface; they are especially visible when their edges sparkle, reflecting the sun's rays. The upper tier clouds are also built from similar ice needles.

Has a special character freezing rain in the form of transparent ice balls from 1 to 3 mm in diameter. These are raindrops frozen in the air. Their loss clearly indicates the presence of a temperature inversion. Somewhere above the earth's surface there is a layer of air with a positive temperature, in which the crystals falling from above melted and turned into droplets, and below it there is a layer with a negative temperature, where the droplets froze.

In the summer, in quite hot weather, sometimes hail falls in the form of more or less large pieces of ice irregular shape(hailstones), from a pea to 5-8 cm in diameter, sometimes more. The weight of hailstones in some cases exceeds 300 g. They often have a heterogeneous structure; they consist of successive transparent and turbid layers of ice. Hail falls from cumulonimbus clouds during thunderstorms and, as a rule, along with heavy rain.

The appearance and size of the hailstones indicate that during their “life” the hailstones are repeatedly carried up and down by strong convection currents, increasing their size by colliding with supercooled drops. In downward currents they descend into layers with positive temperatures, where they melt from above; then they rise up again and freeze from the surface, etc.

For the formation of hailstones, a large amount of water content in the clouds is necessary, which is why hail falls only in the warm season when high temperatures at the earth's surface. Hailfalls are most frequent in temperate latitudes and most intense in the tropics. In polar latitudes, hail is not observed. It happened that hail remained on the ground for a long time in a layer of tens of centimeters. It often harms crops and even destroys them (hail); in some cases, animals and even people can suffer from it.

Precipitation formation

Precipitation occurs if at least some of the elements that make up the cloud (droplets or crystals) become larger for some reason. When cloud elements become so heavy that air resistance and upward movements can no longer keep them suspended, they fall out of the cloud as precipitation.

The enlargement of droplets to the required size cannot occur through condensation. As a result of condensation, only very small droplets are obtained. For larger droplets to form, the condensation process would have to continue for an excessively long time. Larger droplets that fall from a cloud as rain or drizzle can occur in other ways.

Firstly, they may be the result of mutual fusion of droplets. If the droplets are charged differently electric charges, this favors their merger. The difference in droplet sizes is also of great importance. With different sizes, they fall at different speeds and therefore collide more easily with each other. Turbulence also contributes to droplet collisions. This is how drizzle sometimes falls from stratus clouds, and fine and low-intensity rain from powerful cumulus clouds, especially in the tropics, where the liquid water content in the clouds is high.

But heavy precipitation cannot occur through the merging of droplets. For them to fall out, it is necessary that the clouds be mixed, that is, that they contain supercooled droplets and crystals side by side. These are the altostratus, nimbostratus and cumulonimbus clouds. If supercooled droplets and crystals are in mutual proximity, the humidity conditions are such that for droplets we have saturation, and for crystals we have supersaturation. But in this case, the crystals will grow rapidly by sublimation, the amount of water vapor in the air will decrease and for the droplets it will become unsaturated. Therefore, simultaneously with the growth of crystals, evaporation of droplets will occur, i.e., water vapor will be distilled from droplets to crystals.

Enlarged crystals usually begin to fall out from the upper part of the cloud, where they are mainly located. Along the way, they continue to enlarge by sublimation, and in addition, they collide with supercooled droplets, freeze them to themselves and increase in size even more. Droplets frozen upon contact with crystals and crystal fragments greatly increase the number of particles on which crystallization occurs. Thus, large crystals appear in the lower part of the cloud or cloud layer. If the temperature in this lower part of the cloud is above zero, the crystals melt, turning into drops, which fall out of the cloud as rain. The resulting droplets with different falling speeds can coagulate (merge) with each other and with other droplets of the cloud. In other cases, the crystals melt at the base of the cloud and rain also falls. Finally, if the temperature below the clouds is negative all the way to the earth's surface, precipitation falls in the form of snow or pellets. More difficult conditions occur if precipitation falls in the form of hail or freezing rain, but the essence of the phenomenon is the same.

Precipitation can also fall from pure ice clouds, also due to sublimation enlargement of crystals. But usually these clouds are high (in the upper tier) and precipitation from them evaporates without reaching the earth's surface. The “brooms” and “tails” of some types of cirrus clouds are essentially bands of falling precipitation.

Ice and icing

Of particular practical importance is the formation of ice deposits on the earth's surface and on objects as a result of drizzle or rain and the precipitation of heavy fog. This phenomenon is called ice. Ice, therefore, is not released from the air by direct sublimation on ground objects, like the types of solid hydrometeors discussed above. For its formation, the precipitation of supercooled droplets that arise in the atmosphere is necessary.

Ice occurs at not too low negative temperatures (from 0 to -10 - -15°). Precipitation falls in the form of supercooled droplets, but upon contact with the earth's surface or objects, it freezes, covering them with an ice layer. There are transparent and cloudy (matte) ice. The latter occurs with smaller droplets (drizzle) and at lower temperatures. A crust of frozen ice can reach a thickness of several centimeters (and sometimes many centimeters) and cause breakage of branches and breakage of wires; Telegraph poles may fall due to the weight of ice deposited on the wires. Streets and roads can turn into continuous skating rinks. Ice is abundant in mountains in maritime climates; spruce trees in mountain forests are sometimes turned by ice into shapeless blocks.

Ice is often observed in winter in the south European territory Russia. The damage caused by ice to communications and transport makes us especially careful about its forecast.

Subject, class

Geography, 6th grade

Brief summary of the project

The project was developed while studying the topic “Atmosphere”. For two weeks, children collect information material, make a presentation, a booklet, and prepare messages. When working on a project, use different kinds independent work and knowledge control. Children work in groups on problematic issues, conduct research, practical work. At the end of the project they defend their work in the form of a round table.

Questions guiding the project

Fundamental Question

Will it snow or rain tomorrow?

Problematic issues

Why doesn't every cloud rain?

What conditions affect precipitation?

How to determine the weather according to folk signs?

Study questions

List the types of precipitation that you know?

What is a cloud?

What is fog?

Where does the most precipitation occur?

What kind of precipitation falls in our area?

Project plan

Introduction to basic theoretical issues.

Distribution of topics design work students, forming a research plan for the problem.

Search work of students. Preparation of the report in the form of a presentation or booklet

Preparatory stage.

Preparation of the necessary printed materials: (memos on working with reference books, searching for information on the Internet and saving information objects to external media)

Children answer questions, clarify information, discuss the task, and make a general decision on the topic.

Make bookmarks for necessary Internet resources

Main stage. Independent work of groups to complete tasks

Introduce students to the criteria for assessing intermediate and final work.

Organize students to carry out independent research.

Conduct an analysis of the collected material.

Making presentations, compiling booklets.

Excursion to the weather station.

The final stage. Results

Thank everyone who helped with the project.

Post information about the project and its results on the wiki page.

Give a presentation of the project to students.

Take a photo of the final lesson.

Reward the most outstanding students.

Final lesson

Evaluation of participants' work

The compliance of the content with the stated topic, the selection of materials, the logic and consistency of the presentation of the material are assessed

Teacher introductory presentation (publication)

Formative and summative assessment materials

= At the beginning of the project

Questions for conversation